1. Field of the Invention
The present invention relates to a radical polymerizable composition comprising, as one component, an electroconductive polymer having an isothianaphthene structure, which is very stable and is soluble in a general-purpose solvent. More particularly, it relates to a radical polymerizable composition comprising an electroconductive polymer having a .pi.-electron conjugated structure having repeating units of a mono-substituted or di-substituted isothianaphthene structure and a radical polymerizable compound, which is suitable for use in the electric and electronic industries as a material for an electrode of a display element, a material for an electrochromic display element, a circuit material for a printed circuit board, an electrostatic charge accumulation-preventing material, and an electromagnetic shielding material.
2. Description of the Related Arts
Requirements for various electroconductive materials used in the electric and electronic fields are becoming more severe, and the development of electroconductive materials having superior performances such as a good processability, good long-period stability, and high transparency is eagerly desired.
To satisfy these requirements, research has been made into novel electroconductive polymeric compounds to be used in place of conventional carbonaceous and metallic electroconductive materials. Many proposals also have been made on the use of these electroconductive polymeric compounds. Electroconductive polymeric compounds so far proposed include heterocyclic polymers such as polythiophene and polypyrrole, and the use of these polymers as an material for an electrode of a secondary battery or an electrochromic material has been proposed.
Most of these heterocyclic polymers are insoluble and infusible, however, and the molding processability thereof is poor, and thus they cannot be put to practical use.
As the means for overcoming the above problem, some of the present inventors proposed a radical polymerizable composition comprising a compound having .pi.-electron conjugated structure, such as polythiophene or polypyrrole, and a radical polymerizable compound (Japanese Patent Application No. 1-20202).
In this radical polymerizable composition, however, it is difficult to maintain an electroconductive state stably in air.
In connection with polyisothianaphthenes, only insoluble and infusible rigid electroconductive polymers are known, and there are only known a process in which a polymer is formed as a thin film on an electrode plate by electrochemical means (see, for example, Synthetic Metals, Vol. 14, page 45, 1986), and a process in which a polymer is formed as a powder by chemical means using an oxidizing agent (see, for example, Japanese Unexamined Patent Publication No. 63-118323). Known polyisothianaphthenes are characteristically advantageous over other electroconductive polymers in that they are stable in air, are easily doped with ordinary dopants to show a high electroconductivity, and a reversible color change between blue and transparency is shown by electrochemical operations such as doping and dedoping. Nevertheless, because of fatal insoluble and infusible properties, the use of these electroconductive polymers is limited.